This invention relates to television receiver deflection circuits.
In SCR deflection circuits, transient voltages appear across the commutating switch when the switch becomes nonconductive. The magnitude and duration of these voltages are damped, typically by placing a series RC damping network across the switch. Nonetheless, the SCR device in the commutating switch is exposed to rapidly changing voltages when the switch turns off. For B+ voltages of about 270 volts, which are available in many European SCR deflection circuits, the SCR must be fabricated to withstand dv/dt values of from 400V/.mu.s to 1200V/.mu.s.
The resistive component of the RC damping network dissipates considerable power as waste heat, typically from 10 to 15 watts. Optimization of the damping network is difficult, as the dv/dt ratings of the SCR's will vary when obtained from various sources. Thus, optimization of the damping network for an SCR with one dv/dt rating will result in an increased power loss for an SCR with a different dv/dt rating.
It is desirable, therefore, to develop a transient voltage damping network for the commutating switch that results in relatively low dv/dt values and also beneficially uses the power developed in the transient damping network instead of uselessly dissipating the power as waste heat.